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CN-121988373-A - Mesoporous structure-rich ZSM-5 zeolite catalyst, and preparation method and application thereof

CN121988373ACN 121988373 ACN121988373 ACN 121988373ACN-121988373-A

Abstract

The invention relates to a ZSM-5 zeolite catalyst, in particular to a ZSM-5 zeolite catalyst with a mesoporous-rich structure, and a preparation method and application thereof, comprising the following steps of mixing an organic template agent, an alkali source and a silicon source to prepare a silicon source-alkali source aqueous solution; mixing an organic template agent, an alkali source and an aluminum source to prepare an aluminum source-alkali source aqueous solution, adding the aluminum source-alkali source aqueous solution into a silicon source-alkali source aqueous solution to obtain a silicon-aluminum-alkali mixed aqueous solution, ageing the silicon-aluminum-alkali mixed aqueous solution, performing hydrothermal synthesis to obtain a dispersion liquid, separating and drying solids in the dispersion liquid to obtain a precursor, and roasting the precursor to obtain the catalyst. Compared with the prior art, the invention solves the problems of complex preparation process and lower catalyst activity in the prior art. The scheme realizes the convenient synthesis of the ZSM-5 zeolite with high mesoporous content under the condition of low water content, and can efficiently catalyze the low-temperature cracking reaction of plastics.

Inventors

  • TANG YI
  • YAN KEXIN
  • YE ZHAOQI
  • ZHANG YIFAN
  • ZHANG HONGBIN
  • ZHANG YAHONG

Assignees

  • 复旦大学

Dates

Publication Date
20260508
Application Date
20251225

Claims (10)

  1. 1. The preparation method of the ZSM-5 zeolite catalyst with the mesoporous structure is characterized by comprising the following steps of: S1, mixing an organic template agent, an alkali source and a silicon source to prepare a silicon source-alkali source aqueous solution; S2, mixing an organic template agent, an alkali source and an aluminum source to prepare an aluminum source-alkali source aqueous solution; S3, adding the aluminum source-alkali source aqueous solution prepared in the step S2 into the silicon source-alkali source aqueous solution prepared in the step S1 to obtain a silicon-aluminum-alkali mixed aqueous solution; s4, separating and drying the solid in the dispersion liquid obtained in the step S3 to obtain a ZSM-5 zeolite catalyst precursor with a mesoporous structure; and S5, roasting the precursor obtained in the step S4 to obtain the catalyst.
  2. 2. The method for preparing the ZSM-5 zeolite catalyst with the mesoporous structure according to claim 1, wherein, The organic template agent is one or more of tetrapropylammonium hydroxide, tetrapropylammonium chloride and tetrapropylammonium bromide; The alkali source is one or more of tetrapropylammonium hydroxide, sodium hydroxide and potassium hydroxide; The silicon source is one or more of silica sol, white carbon black, silica gel, potassium silicate and tetraethyl silicate; The aluminum source is one or more of aluminum foil, aluminum powder, aluminum hydroxide, aluminum chloride and aluminum sulfate.
  3. 3. The method for preparing the ZSM-5 zeolite catalyst with the mesoporous structure according to claim 1, wherein, The concentration of the organic template agent in the silicon source-alkali source aqueous solution is 2-5 mol/L, and the concentration of the organic template agent in the aluminum source-alkali source aqueous solution is 2-5 mol/L; The concentration of the alkali source in the silicon source-alkali source aqueous solution is 2-5 mol/L, and the concentration of the alkali source in the aluminum source-alkali source aqueous solution is 2-5 mol/L; The mass concentration of the silicon source in the silicon source-alkali source aqueous solution is 20-50wt%; The mass concentration of the aluminum source in the aluminum source-alkali source aqueous solution is 2-5 wt%.
  4. 4. The method for preparing the mesoporous structure-rich ZSM-5 zeolite catalyst according to claim 1, wherein in the step S3, the temperature of the hydrothermal synthesis is 120-200 ℃, and the time of the hydrothermal synthesis is 2-10 days.
  5. 5. The preparation method of the mesoporous-structure-enriched ZSM-5 zeolite catalyst according to claim 1, wherein in the step S4, centrifugation is adopted, the centrifugation speed is 8000-12000 rpm, the centrifugation time is 3-50 minutes, the drying temperature is 60-100 ℃, and the drying time is 6-24 hours.
  6. 6. The method for preparing a mesoporous structure-rich ZSM-5 zeolite catalyst according to claim 1, wherein in the step S5, the roasting temperature is 300-900 ℃, and the roasting time is 3-12 hours.
  7. 7. A mesoporous-rich structure ZSM-5 zeolite catalyst, characterized in that it is obtained by the preparation method according to any one of claims 1 to 6; the catalyst has loose morphology formed by stacking multiple particles.
  8. 8. The ZSM-5 zeolite catalyst of a mesoporous structure according to claim 7, wherein the catalyst has a ZSM-5 topology in which at least 80% is mesoscopic crystals packed by packed unit particles; the particle size of the stacking unit particles is 10-20 nanometers, and the particle size of the mesoscopic crystal is 50-150 nanometers.
  9. 9. The ZSM-5 zeolite catalyst according to claim 7 in which the catalyst is in the form of a mesoporous structure, The total pore volume of the catalyst is not less than 0.5 cubic centimeters per gram; the mesoporous volume of the catalyst is 0.5-1 cubic centimeter per gram; The total specific surface area of the catalyst is not less than 350 square meters per gram; the external specific surface area of the catalyst is not less than 150 square meters per gram; the ratio of the external specific surface area of the catalyst to the total specific surface area is not less than 30%.
  10. 10. Use of the mesoporous structure-rich ZSM-5 zeolite catalyst as claimed in claim 9 in a high molecular polymer cracking reaction.

Description

Mesoporous structure-rich ZSM-5 zeolite catalyst, and preparation method and application thereof Technical Field The invention relates to a ZSM-5 zeolite catalyst, in particular to a ZSM-5 zeolite catalyst with a mesoporous structure, a preparation method and application thereof. Background Zeolite molecular sieve is a material with regular microporous structure, and is widely applied to the fields of petrochemical industry, fine chemical industry, daily chemical industry and the like due to the unique shape selective catalysis and adsorption performance, and is often used as a catalyst, an adsorbent and an ion exchanger. However, the conventional zeolite molecular sieve is limited by narrow microporous channels, has the problems of insufficient exposure of active sites, high mass transfer resistance, easy deactivation of carbon deposition and the like, and has poor performance in macromolecular reactions (such as plastic catalytic cracking). To overcome the above limitations, a multi-pore zeolite has been developed. By introducing the mesoporous structure, the external specific surface area can be obviously increased, and the accessibility of the active site is improved, so that the macromolecule conversion efficiency is improved. At present, the method for constructing mesoporous zeolite mainly comprises a direct synthesis method from bottom to top and a post-treatment method from top to bottom. The former usually depends on expensive templates or hard templates, the cost is to be optimized, the process flow is long, and the latter involves processes of etching, stripping and the like, so that the zeolite crystal structure is easy to damage, and the atom economy is poor. Therefore, the development of an economical, green and efficient synthetic route for mesoporous zeolites remains an important topic in the art. In the prior art, as CN106673008B discloses a method for synthesizing a ZSM-5 zeolite molecular sieve with a multilevel structure of intra-crystal mesopores and inter-crystal mesopores, and a synthesis method and application thereof. The ZSM-5 zeolite molecular sieve with the multilevel structure has inter-crystal mesopore and intra-crystal mesopore structures besides micropores with a zeolite structure, wherein the size of primary nano-crystal particles is 40-500 nm, and the size of secondary stacked particles is 500-5 mu m. The preparation method comprises the steps of mixing a silicon source, an aluminum source, an alkali source, a crystallization inducer, an auxiliary agent and water to obtain crystallization gel, crystallizing the crystallization gel under a hydrothermal condition, washing, filtering, drying and roasting to obtain the mesoporous ZSM-5 molecular sieve, wherein the silicon source is magadiite, the crystallization inducer is an organic ammonium salt and a seed crystal, and the auxiliary agent is at least one of alcohol or amine. However, in the prior art, a complex pretreatment process is required, and crystals are built by adding seed crystals, so that the overall preparation method is complex, and the prepared ZSM-5 zeolite molecular sieve has large stacking unit particles (primary particles) or final products (secondary particles), so that the activity of the ZSM-5 zeolite molecular sieve still has defects. In industrial zeolite production, low water systems are favored because of the significant increase in single-pot yields and reduced energy consumption. The xerogel conversion method can further save water, but still depends on a large amount of solvents to assist the gelation and crystallization process. Although the solvent-free method has potential, the solvent-free method is limited by the problems of limited types of synthesizable zeolite, dependence on seed crystals, complex process (such as ball milling), poor equipment suitability and the like, and the large-scale application is difficult to realize. In summary, the existing synthesis method of mesoporous ZSM-5 generally has the problems of complex process, high cost, insufficient environmental friendliness and the like. Therefore, there is an urgent need in the art to develop a method for synthesizing ZSM-5 zeolite with high mesoporous content in high yield by a simple process under the condition of low water content, and to make the ZSM-5 zeolite have high catalytic activity and product yield in macromolecular reactions such as low-temperature cracking of plastics. Disclosure of Invention The invention aims to solve at least one of the problems, and provides a ZSM-5 zeolite catalyst with a mesoporous structure, a preparation method and application thereof, so as to solve the problems of complex preparation process and low catalyst activity in the prior art. The scheme realizes the convenient synthesis of the ZSM-5 zeolite with high mesoporous content under the condition of low water content, and can efficiently catalyze the low-temperature cracking reaction of plastics. The aim of the invention is achieved by the